The present disclosure relates to a data structure of a branch-structured vector data, a branch-structured vector data editing apparatus, a branch-structured vector data editing program recorded on a computer-readable recording medium, an embroidery data creation apparatus, and an embroidery data creation program recorded on a computer-readable recording medium, each of which may handle a plurality of thread colors and loop-shaped embroidery trajectories.
Conventionally, in order to embroider an image expressed as an image data, an embroidery data creation apparatus that creates embroidery data controls a needle in an embroidery sewing machine. For example, in an embroidery sewing machine disclosed in Japanese Patent Application Laid-Open Publication No. Hei 8-38756, a boundary line that defines a closed region of an image is first extracted from image data and subjected to line thinning processing. Then, based on the results of this processing, tree structure data is created, which is a tree structure version of embroidery trajectories. Such tree structure data is a set of vectors that indicate directions and lengths of needle strokes. Based on this tree structure data, underlying stitch sewing data (“running stitch sewing data” in the present disclosure) and stitch sewing data are created. Underlying stitch sewing (“running stitch sewing” in the present disclosure) refers to sewing that is performed in accordance with underlying stitch sewing data. Underlying stitch sewing is performed at a place, which will be hidden under stitch sewing (sewing that is performed in accordance with stitch sewing data), that forms a final embroidery result, in order to sew embroidery as in the case of single-stroke drawing, so that a thread may not be cut off or jump to a distant sewing position as much as possible. That is, underlying stitch sewing is covered by stitch sewing, thereby to complete an embroidery.
In this conventional embroidery data creation apparatus, the tree structure data is created for each of the thread colors. For example, in the case of embroidering with red and green threads, tree structure data of a red branch and of a green branch are created. Further, in some cases, rather than creating embroidery data directly from the tree structure data that was created from image data, an image and a vector of an embroidery result created from the tree structure data are displayed on a display screen, which are in turn edited by adding, deleting, or changing a vector (embroidery) in accordance with an instruction entered by a user. It should be noted that “changing” as referred to in this description includes changing a sewing method, moving an endpoint of a vector (node), changing of an inter-node path, changing a thickness, expanding, reducing and changing of a thread color.